1. Field of the Invention
The present invention relates to an intake manifold and an engine including the intake manifold.
2. Description of Related Art
Intake manifolds are known that include a surge tank and an intake passage part communicating with the surge tank and fixed to the cylinder head of the engine. For example, there are such intake manifolds into which blowby gas generated inside the crankcase of the engine is introduced. Since blowby gas contains oil and water, such fluid may accumulate inside the intake passage part of the intake manifold. If a large amount of such fluid is accumulated inside the intake passage part, depending on the operation state of the engine, a large amount of fluid may be suctioned at once by intake air into the combustion chamber of the engine, which will affect the operation state of the engine.
Therefore, in Japanese Patent Application Publication No. 2013-177869, to prevent the accumulation of a large amount of fluid inside the intake passage part, the passage sectional area of the intake passage part is gradually reduced from the upstream side toward the bottom part so as to increase the flow velocity of intake air, and thus the efficiency of suctioning the fluid into the combustion chamber of the engine is enhanced.